Chair back



FIG. 1 is a front perspective view of a chair back showing our newdesign;

FIG. 2 is a rear perspective view thereof;

FIG. 3 is a front elevational view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a left side view thereof;

FIG. 7 is a top plan view thereof; and,

FIG. 8 is a bottom plan view thereof, wherein the broken lines are forthe purpose of illustrative purposes, showing the environment in whichthe design is used, and forms no part of the design.

CLAIM The ornamental design for a chair back, as shown and described.